/*
** $Id: lzio.c,v 1.31.1.1 2007/12/27 13:02:25 roberto Exp $
** a generic input stream interface
** See Copyright Notice in lua.h
*/


#include <string.h>

#define lzio_c
#define LUA_CORE

#include "lua.h"

#include "llimits.h"
#include "lmem.h"
#include "lstate.h"
#include "lzio.h"


int luaZ_fill(ZIO *z)
{
    size_t size;
    lua_State *L = z->L;
    const char *buff;
    lua_unlock(L);
    buff = z->reader(L, z->data, &size);
    lua_lock(L);
    if (buff == NULL || size == 0) return EOZ;
    z->n = size - 1;
    z->p = buff;
    return char2int(*(z->p++));
}


int luaZ_lookahead(ZIO *z)
{
    if (z->n == 0)
    {
        if (luaZ_fill(z) == EOZ)
            return EOZ;
        else
        {
            z->n++;  /* luaZ_fill removed first byte; put back it */
            z->p--;
        }
    }
    return char2int(*z->p);
}


void luaZ_init(lua_State *L, ZIO *z, lua_Reader reader, void *data)
{
    z->L = L;
    z->reader = reader;
    z->data = data;
    z->n = z->i = 0;
    z->p = NULL;
}


/* --------------------------------------------------------------- read --- */
size_t luaZ_read(ZIO *z, void *b, size_t n)
{
    while (n)
    {
        size_t m;
        if (luaZ_lookahead(z) == EOZ)
            return n;  /* return number of missing bytes */
        m = (n <= z->n) ? n : z->n;  /* min. between n and z->n */
        if (b)
            memcpy(b, z->p, m);
        z->n -= m;
        z->i += m;
        z->p += m;
        if (b)
            b = (char *)b + m;
        n -= m;
    }
    return 0;
}

/* ------------------------------------------------------------------------ */
char *luaZ_openspace(lua_State *L, Mbuffer *buff, size_t n)
{
    if (n > buff->buffsize)
    {
        if (n < LUA_MINBUFFER) n = LUA_MINBUFFER;
        luaZ_resizebuffer(L, buff, n);
    }
    return buff->buffer;
}


